1. Field of the Invention
This invention relates to a sprocket configuration and, more particularly, to a chain drive sprocket having a novel tooth and pocket profile.
2. Description of the Prior Art
In vehicle chain drives, such as those found in crawler tractors having a track comprised of interconnected track links, the track is driven and guided by a drive sprocket. The sprocket has a plurality of teeth defining a predetermined pitch and also defining pockets between adjacent teeth into which the track bushings are received as they are driven by the teeth.
In one conventional sprocket configuration, the sprocket root surface, at least partially defining the pocket between adjacent teeth, is cylindrical in shape and is either equal to or slightly larger than the diameter of the track bushing. Conventionally, such root surfaces either extend outwardly to the peripheral surface of the sprocket or merge with a linear surface, which, in turn, merges with a topping surface extending to the outer periphery of the sprocket.
The environment in which such sprockets and track-type chains are employed usually results in the accumulation of foreign matter in the pocket which tends to urge the chain outwardly from the bottom root surface of the pocket and causes the chain bushing to ride out on the tooth face away from the bottom root area thereby causing an elongation of the chain during driving operation. This outward movement of the chain relative to the pocket causes the bushing to make contact with the outer portions of the sprocket teeth causing undesirable wear of the bushings.
It is further recognized that a certain amount of so-called "backlash" is an inherent feature in chain drives. This backlash is the distance that the bushing will move within the pocket between forward rotation of the sprocket and reverse rotation of the sprocket. The amount of backlash is usually a specified amount that is based upon a number of factors, such as the wrap angle of the chain about the sprocket, or the amount of buildup allowance that is designed into the sprocket. In order to prevent excessive wear of the sprocket, allowance must be made both for the buildup between the bushing and the root surface and for backlash so that track jumping problems and break-in wear are reduced.